Thermally shrinkable films made of polystyrene resins have been widely used in labels for PET bottles. Additionally, laminated films with front and back layers of polyester resins and an intermediate layer of a polystyrene resin and laminated films with adhesion layers in between these layers have been proposed.
Examples of this type of art include those described in the below-indicated patent documents. However, for laminated films with adhesive layers in between, a step of forming the adhesive layers is needed, and thus the costs were high, and there was also the risk of the adhesive layers being incapable of following film shrinkage, which results in stripping. On the other hand, for laminated films without adhesive layers in between, while a certain degree of interlayer adhesion strength can be obtained by selecting specific resins, interlayer adhesion strength was still insufficient when used under conditions of actual use.